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Microglial peri-somatic abutments classify two novel types of GABAergic neuron in the inferior colliculus

Lookup NU author(s): Dr Llwyd Orton

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Abstract

© 2020 The Authors. European Journal of Neuroscience published by Federation of European Neuroscience Societies and John Wiley & Sons LtdEmerging evidence suggests functional roles for microglia in the healthy, mature nervous system. However, we know little of the cellular density and ramified morphology of microglia in sensory systems, and even less of their inter-relationship with inhibitory neurons. We therefore conducted fluorescent multi-channel immunohistochemistry and confocal microscopy in guinea pigs of both sexes for Iba1, GAD67, GFAP, calbindin, and calretinin. We explored these markers in the inferior colliculi (IC), which contain sub-regions specialized for different aspects of auditory processing. First, we found that while the density of Iba1+ somata is similar throughout the IC parenchyma, Iba1+ microglia in dorsal cortex are significantly more ramified than those in the central nucleus or lateral cortex. Conversely, Iba1+ ramifications in ventral central nucleus, a region with the highest density of GAD67+ (putative GABAergic) neurons in IC, are longer with fewer ramifications. Second, we observed extensive abutments of ramified Iba1+ processes onto GAD67+ somata throughout the whole IC and developed novel measures to quantify these. Cluster analyses revealed two novel sub-types of GAD67+ neuron that differ in the quantity of Iba1+ somatic abutments they receive. Unlike previous classification schemes for GAD67+ neurons in IC, these clusters are not related to GAD67+ soma size. Taken together, these data demonstrate that microglial ramifications vary between IC sub-regions in the healthy, adult IC, possibly related to the ongoing demands of their niche. Furthermore, Iba1+ abutments onto neuronal somata are a novel means by which GAD67+ neurons can be classified.

Publication metadata

Author(s): Webb SD, Orton LD

Publication type: Article

Publication status: Published

Journal: European Journal of Neuroscience

Year: 2021

Volume: 54

Issue: 5

Pages: 5815-5833

Print publication date: 01/09/2021

Online publication date: 05/12/2020

Acceptance date: 20/05/2020

Date deposited: 16/02/2021

ISSN (print): 0953-816X

ISSN (electronic): 1460-9568

Publisher: Blackwell Publishing Ltd

URL: https://doi.org/10.1111/ejn.15075

DOI: 10.1111/ejn.15075

PubMed id: 33278847

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